title: Contribution of Bcl-2 phosphorylation to Bak binding and drug resistance.
abstract: Bcl-2 is phosphorylated on Ser(70) after treatment of cells with spindle poisons. On the basis of effects observed in cells overexpressing Bcl-2 S70E or S70A mutants, various studies have concluded that Ser(70) phosphorylation either enhances or diminishes Bcl-2 function. In the present study, the ability of phosphorylated Bcl-2, as well as the S70E and S70A mutants, to bind and neutralize proapoptotic Bcl-2 family members under cell-free conditions and in intact cells was examined in an attempt to resolve this controversy. Surface plasmon resonance indicated that phosphorylated Bcl-2, Bcl-2 S70E, and Bcl-2 S70A exhibit enhanced binding to Bim and Bak compared with unmodified Bcl-2. This enhanced binding reflected a readily detectable conformation change in the loop domain of Bcl-2. Furthermore, Bcl-2 S70E and S70A bound more Bak and Bim than wild-type Bcl-2 in pull-downs and afforded greater protection against several chemotherapeutic agents. Importantly, binding of endogenous Bcl-2 to Bim also increased during mitosis, when Bcl-2 is endogenously phosphorylated, and disruption of this mitotic Bcl-2/Bim binding with navitoclax or ABT-199, like Bcl-2 downregulation, enhanced the cytotoxicity of paclitaxel. Collectively, these results provide not only a mechanistic basis for the enhanced antiapoptotic activity of phosphorylated Bcl-2, but also an explanation for the ability of BH3 mimetics to enhance taxane sensitivity.
authors.affiliation: Division of Oncology Research, Department of Oncology, Mayo Clinic, Rochester, MN 55905.|Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905.
authors.forename: Haiming
authors.initials: H
authors.lastname: Dai
authors.affiliation: Division of Oncology Research, Department of Oncology, Mayo Clinic, Rochester, MN 55905.
authors.forename: Husheng
authors.initials: H
authors.lastname: Ding
authors.affiliation: Division of Oncology Research, Department of Oncology, Mayo Clinic, Rochester, MN 55905.|Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905.
authors.forename: X Wei
authors.initials: XW
authors.lastname: Meng
authors.affiliation: Division of Oncology Research, Department of Oncology, Mayo Clinic, Rochester, MN 55905.
authors.forename: Sun-Hee
authors.initials: SH
authors.lastname: Lee
authors.affiliation: Division of Oncology Research, Department of Oncology, Mayo Clinic, Rochester, MN 55905.
authors.forename: Paula A
authors.initials: PA
authors.lastname: Schneider
authors.affiliation: Division of Oncology Research, Department of Oncology, Mayo Clinic, Rochester, MN 55905.|Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905.
authors.forename: Scott H
authors.initials: SH
authors.lastname: Kaufmann
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D000072224:Bcl-2-Like Protein 11; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D002478:Cells, Cultured; D004353:Drug Evaluation, Preclinical; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics; D006801:Humans; D019169:Jurkat Cells; D020014:K562 Cells; D008565:Membrane Proteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D011485:Protein Binding / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C494772:BAK1 protein, human; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D050998:bcl-2 Homologous Antagonist-Killer Protein; D016203:CDC2 Protein Kinase